Since the phenomena of self-initiated smoking cessation remains relatively unstudied, the proposed research is studying the efficacy of an adult smoking cessation program comprising mail and telephone contacts over a 12-month period both with and without a more intensive intervention involving feedback on expired carbon monoxide level. It is hypothesized that when maintained over a long term, even a minimal intervention program will produce significantly increased cessation rates as compared to the "natural" cessation rate observed in a control group and that this effect can be enhanced by a single face-to-face session. As of December 12, 1980, fifteen hundred and seventy-seven households with one or more smokers have been selected from a population sample and randomly assigned to: (1) periodic mail and telephone contact over a 12-month period plus initial face-to-face biochemical feedback, (2) periodic mail and telephone contacts only, (3) initial face-to-face biochemical feedback only, (4) a control condition involving a minimal pretreatment telephone contact. The interest of smokers in a wide array of self-treatment materials is being assessed. The 12 months of mail and telephone contacts will be completed during Year 2 of the study and the smoking status of all subjects (1600 primary subjects plus about 600 additional smokers who live with primary subjects) will be assessed biochemically at the end of the treatment phase and at a 12-month follow-up.